title: Dissociable perceptual-learning mechanisms revealed by diffusion-model analysis.
abstract: Performance on perceptual tasks improves with practice. Most theories address only accuracy data and tacitly assume that perceptual learning is a monolithic phenomenon. The present study pioneers the use of response time distributions in perceptual learning research. The 27 observers practiced a visual motion-direction discrimination task with filtered-noise textures for four sessions with feedback. Session 5 tested whether the learning effects transferred to the orthogonal direction. The diffusion model (Ratcliff, Psychological Review, 85, 59-108, 1978) achieved good fits to the individual response time distributions from each session and identified two distinct learning mechanisms with markedly different specificities. A stimulus-specific increase in the drift-rate parameter indicated improved sensory input to the decision process, and a stimulus-general decrease in nondecision time variability suggested improved timing of the decision process onset relative to stimulus onset (which was preceded by a beep). A traditional d' analysis would miss the latter effect, but the diffusion-model analysis identified it in the response time data.
authors.affiliation: Department of Psychology, Ohio State University, 200B Lazenby Hall, Columbus, OH 43210, USA. apetrov@alexpetrov.com
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Petrov
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Van Horn
authors.forename: Roger
authors.initials: R
authors.lastname: Ratcliff
mesh_terms: D004192:Discrimination, Psychological; D006801:Humans; D007858:Learning / Q000502:physiology; D008960:Models, Psychological; D009038:Motion; D009039:Motion Perception; D010775:Photic Stimulation; D011930:Reaction Time; D014796:Visual Perception